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Recent content by 271828

  1. 271828

    Vibration of WF Beam Girders Supporting Steel Joists for Banquet Hall

    I have heard numbers like 6 in. quite a few times. The experience of the acceleration is pretty extreme, so the person would swear on a stack of Bibles that the floor is moving several inches. An amazing number is the displacement amplitude corresponding to the 0.5%g limit for offices and...
  2. 271828

    Vibration of WF Beam Girders Supporting Steel Joists for Banquet Hall

    The floor will vibrate mostly at its natural frequency, not the frequency of the dancers' movements. 5 Hz is a fairly low value for natural frequency. The lowest (not quite) believable natural frequency is 2 Hz. The displacement amplitude corresponding to 50%g would be (0.5*386 in./s^2) / (2 *...
  3. 271828

    Vibration of WF Beam Girders Supporting Steel Joists for Banquet Hall

    Yeah, I get that the motion was extreme, but 6 in.? 50%g at 5 Hz would be 0.2 in.
  4. 271828

    Vibration of WF Beam Girders Supporting Steel Joists for Banquet Hall

    Surely you're using hyperbole! 50%g at 5 Hz equates to the following displacement amplitude: (0.5 * 386) / (2*pi*5)^2 = 0.2 in.
  5. 271828

    Vibration of WF Beam Girders Supporting Steel Joists for Banquet Hall

    The recommended limit if the floor only supports dancers would be 4-7%g. They will tolerate pretty high accelerations. Seated people tolerate much less. Thus, if diners are a possibility, the limit is 1.5-2.5%g. If Design Guide 11 is saying 118%g, then the floor would probably have severe...
  6. 271828

    Vibration of WF Beam Girders Supporting Steel Joists for Banquet Hall

    I don't think there's any way to answer your last sentence, other than to guess. You might get lucky and then again you might not. I'd make sure my floor is satisfies the check. The Chapter 5 rhythmic groups method has been around a long time. The industry has about 30 years of experience with it.
  7. 271828

    Vibration of WF Beam Girders Supporting Steel Joists for Banquet Hall

    Natural frequency is overwhelmingly dominant for rhythmic groups. 5.19 Hz isn't very high. The second harmonic of the force is up to 5.4 Hz according to Design Guide 11 Table 5-2. If you can get the natural frequency a bit above 5.4 Hz, you'll have a decent shot. You could try to make the...
  8. 271828

    Digital Seal and Signature

    When I read this, it reminded me of Better Call Saul when Jimmy doctored his brother's legal paperwork. I know that was totally off-topic and not helpful to the current conversation. LOL
  9. 271828

    Compact, non compact section properties as per AISC 2005

    The next question is whether STAAD correctly handled a section with slender elements. The default assumption is it does not. Verify before relying on its results.
  10. 271828

    Valid Pin Boundary Condition?

    It would be interesting to see the moment diagram if you rerun this with fixed bases.
  11. 271828

    Valid Pin Boundary Condition?

    The critical force effect in most frames like the OP's would be the moment at the top of the column, and a fixed base assumption just made that a lot smaller. Thus, you need to show the base plate is thick enough to justify fixed. What's the method for that? Note that for flush moment end...
  12. 271828

    Valid Pin Boundary Condition?

    How would you model and design the base plate in the OP's case?
  13. 271828

    Valid Pin Boundary Condition?

    With realistic stiffness at the left base plate, the left column would have a small moment at the base and slightly less than 4500 at the top. The column design would not be appreciably affected. Great example of why we can use a pin.
  14. 271828

    Valid Pin Boundary Condition?

    Consider a simple shear connection between a beam and column. The beam will have an end moment that is ignored for the most part. That moment will be small if the connection is detailed correctly, such as a double angle with non-thick legs. Your base plate is kinda like that. If you don't...
  15. 271828

    Do you guys defer steel connections? Should it be on the contact?

    W8x10 and W10x12 are almost always very short, so little of the cost is from tonnage. The weight difference is small between those and W12x14, which almost never causes any connection difficulty. I used to be an EOR and have worked as a connection designer in recent years. Knowing what I know...
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